Power distribution systems serve the purpose of supplying power to components in a computer systems. Most personal computers can be plugged into a standard electrical outlet. The power distribution system supply pulls the required amount of power and converts the power from an alternating current (AC) domain to a direct current (DC) domain. It also regulates the voltage and current to eliminate spikes and surges common in most electrical systems. Not all power supplies, however, perform an adequate job in regulation, thus a computer is often susceptible to large current fluctuations.
With today's highly sensitive electronic equipment, internal current surges play a significant role in the deterioration of that equipment. Proper power protection is important for protecting components from the immediate and long-term effects of current surge damage. The drawback of protection circuits used in the past were that they required a current sensor and a control circuit to monitor and regulate the amount of current in the system. The current sensor and control circuit required additional physical space and cost that were undesirable.